US-12617160-B2 - Variable frequency microwave joining

Abstract

Bonded untreated plastic substrates and process for manufacturing same, including a variable frequency microwave and variable frequency microwave active welding paste. Use of 1-component variable frequency microwave cured paste adapted to wet and bond untreated plastic substrates that is operable to reduce production cycle time, reduce production costs, reduce operating costs, and reduce production line space. Hardening of the welding paste allows joining of thermoplastic panels quickly without the need for panel surface treatment. Polypropylene substrate bonding with 1-component epoxy adhesive that is variable frequency microwave reactive, wherein the substrates are untreated.

Inventors

• Marek Pospisek
• Zdenek Severa

Assignees

• MAGNA EXTERIORS INC.

Dates

Publication Date

20260505

Application Date

20231030

Claims (19)

1. 1 . A substrate adapted for a vehicle, comprising: a first panel formed of a first plastic material; a second panel formed of the first plastic material or a second plastic material that is different than the first plastic material, said first and second panels are untreated at a plurality of joining areas; and a predetermined 1-component VFM reactive welding paste located on said joining areas and hardened by VFM to thereby join said first and second panels together; multiple ribs on each of said first and second panels, the ribs extend outwardly from the first and second panels and are operable to allow VFM curing of the welding paste faster, a first rib plane of said ribs on said first panel is spaced from a second rib plane of said ribs on said second panel such that the ribs of said first panel do not overlap the ribs of said second panel along said first and second rib planes and said 1-component VFM reactive welding paste is located between said first and second rib planes and between respective adjacent ribs along said first and second panels.
2. 2 . The substrate of claim 1 , wherein the first and second panels are thermoplastic panels adapted for an exterior of a vehicle.
3. 3 . The substrate of claim 1 wherein the ribs of the first panel are provided on a minority of a surface area of the joining area of the first panel, and the ribs of the second panel are provided on a minority of a surface area of the joining area of the second panel.
4. 4 . The substrate of claim 1 wherein the 1-component VFM reactive welding paste is at least 4 mm thick in a direction extending between the first panel and second panel.
5. 5 . A method of bonding substrates adapted for a vehicle, comprising: providing a Variable Frequency Microwave (VFM) machine; providing a first plastic material for forming a first panel; providing material for forming a second panel, where the material for forming the second panel is the same as the first plastic material or is a second plastic material that is different than the first plastic material; providing a 1-component epoxy VFM cured welding paste; forming the first and second panels with a ribs formed on both of the first panel and the second panel, said ribs operable to help to weld said first and second panels with said welding paste faster and with predetermined higher force; applying the welding paste in at least one location on the first panel and/or second panel where a joining of the first and second panels is desired; aligning the first and second panels with the welding paste in contact with said first and second panels, wherein a first rib plane of said ribs on said first panel is spaced from a second rib plane of said ribs on said second panel such that said first panel ribs do not overlap said second panel ribs along said first and second rib planes and said 1-component VFM cured welding paste is located between said first and second rib planes and between respective adjacent ribs along said first and second panels; and applying predetermined VFM (microwaves) to achieve a predetermined temperature to harden the welding paste to join the first and second panels.
6. 6 . The method of claim 5 , wherein the welding paste includes microwave absorbent material.
7. 7 . The method of claim 5 , wherein the first and second panels are thermoplastic panels adapted for an exterior of a vehicle.
8. 8 . The method of claim 5 , wherein the welding paste is hardened to allow the joining of the first and second panels in about 20 seconds.
9. 9 . The method of claim 5 , wherein the first and second panels are not surface treated prior to application of the welding paste and joining.
10. 10 . The method of claim 5 , wherein the predetermined temperature is between 180 to 270 degrees Celsius.
11. 11 . The method of claim 5 , wherein the welding paste includes at least one additive adapted to act as a softener.
12. 12 . The method of claim 5 , wherein the first and second panels are thermoplastic panels.
13. 13 . The method of claim 5 , wherein the first and second panels are polypropylene panels.
14. 14 . The method of claim 5 , wherein the first and second panels are thermoplastic liftgate panels adapted for a vehicle.
15. 15 . The method of claim 5 , wherein the first and second panels are exterior panels or module panels adapted for a vehicle.
16. 16 . The method of claim 5 , wherein the welding paste can withstand up to at least about 270 degrees Celsius.
17. 17 . The method of claim 5 , further comprising a predetermined tool nest adapted to hold the first and second panels under predetermined pressure or force during curing of the welding paste via variable frequency microwave (VFM) joining.
18. 18 . A method of bonding substrates adapted for a vehicle, comprising: providing at least one first panel formed of a first plastic material and including at least one untreated joint area that includes attachment features in the form of ribs extending outwardly from an inner surface of the at least one first panel; providing at least one second panel formed of the first plastic material or other a plastic material and including at least one untreated joint area that includes attachment features in the form of ribs projecting outwardly from an inner surface of the at least one second panel; providing a VFM reactive welding paste; applying the welding paste in at least one untreated joint area on the first panel and/or second panel operable for joining the first and second panels; aligning the first and second panels with the welding paste in contact with said first and second panels and holding in contact, wherein a first attachment feature plane of said attachment features on said first panel is spaced from a second attachment feature plane of said attachment features on said second panel such that said first panel attachment features do not overlap said second panel attachment features along said first and second attachment feature planes and said VFM reactive welding paste is located between said first and second attachment feature planes and between respective adjacent attachment features along said first and second panels; applying predetermined VFM (microwaves) to achieve a predetermined temperature to harden the welding paste to join the first and second panels.
19. 19 . The method of claim 18 , wherein the welding paste is a 1-component epoxy resin curable by VFM.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Non-Provisional patent application and claims benefit of U.S. Provisional Patent Application No. 63/420,153, filed Oct. 28, 2022. The disclosures of the above application are incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to a variable frequency microwave (VFM) joining, in particular bonding untreated plastic substrate. BACKGROUND OF THE INVENTION Common adhesive that must be cured for joining panels is known to be problematic. Accordingly, there is a need for features on at least one panel in combination with variable frequency microwave joining operable to help weld plastic panels with predetermined paste faster and with higher force to provide a properly sealed connection, eliminate bond-line read through, match thermoplastic properties of materials, and reduce costs and manufacturing space. SUMMARY OF THE INVENTION The present invention is directed to bonded untreated plastic substrates and process for manufacturing same, including a variable frequency microwave and variable frequency microwave active welding paste operably adapted to achieve a predetermined lean assembly process, significantly reduce footprint of predetermined assembly equipment, reduce capital and predetermined tooling costs, and simplify assembly processes. Use of 1-component variable frequency microwave cured paste adapted to wet and bond untreated plastic substrates that is operable to reduce production cycle time, reduce production costs, reduce operating costs, and reduce production line space. Hardening of the welding paste allows joining of thermoplastic panels quickly without the need for panel surface treatment. Polypropylene substrate bonding with 1-component epoxy adhesive that is variable frequency microwave reactive, wherein the substrates are untreated. The present invention is generally directed to substrate bonding, e.g., welding, liftgate panels welding, automotive parts bonding line, etc. In particular, welding via variable frequency microwave joining (VFM) reactive paste. The present invention incorporates a predetermined suitable adhesive, e.g., welding paste, 1-component epoxy resin, compounded with fillers and additives for desired mechanical properties. This novel method of hybrid welding via reactive paste ensures that low surface energy substrates such as polypropylene can form high performance structural joints without additional surface preparation. In accordance with aspects of the present invention, it is found that VFM (microwaves) in the range of 5.8 to 6.2 GHz are able to rapidly increase the temperature of microwave absorbent material (welding paste) within a few seconds without absorbing in to neither the substrates nor surrounding fixturing. Heat absorbed by paste melts the substrate in contact with the paste and the adhesive paste merges with the melted substrate forming the join similar to the weld of thermoplastic material. Hardening of the welding paste allows joining of thermoplastic panels in a very short time (e.g., about 20 seconds), without the need for additional processes as a solvent cleaning and panel surface treatment (plasma, flaming, primer, adhesion promoter) that are traditionally required in thermoplastic bonding process. Technology requirements in accordance with aspects of the present invention include that a new generation of VFM machine is developed as well as VFM active welding paste. Benefits in accordance with aspects of the present invention include achieving a lean assembly process, significantly reduced footprint of the assembly equipment, capital and tooling cost, and simplified assembly process. In addition, the present invention's VFM joint is different than a common adhesive joint for at least the reasons that the present invention includes ribs on each panel on the join area of each panel that reduces welding time and increases strength of join and that helps weld plastic panels with paste faster and with higher force. The present invention of 1-component epoxy resin compound also offers possibility to join different material combinations of thermoplastic materials. Furthermore, 1-component epoxy resin is compounded with modified rubbers with terminal carboxyl groups, polypropylene filler and polypropylene glycol to provide flexible join as well as similar CLTE between the substrates and paste. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: FIGS. 1-2 are cross sections of an exemplary substra